1. Field of the Invention
The present invention relates to a rotary drum device having a brush for supplying a current or a signal to a drum rotating portion of a VTR.
2. Description of the Related Art
Conventional rotary drum devices employ a combination of a brush and a slip ring as a mechanism for supplying a current or a signal to a rotary portion of the drum. FIGS. 1(a) and 1(b) are respectively plan and front views of a conventional drum unit.
The drum unit shown in FIG. 1 includes a bottom drum 8, a top drum 9 rotatably mounted on the bottom drum 8, a motor unit 10 for supplying a rotational force to the top drum 9 through a shaft (not shown), a slip ring unit 11 connected to a circuit (not shown) on the top drum 9, a brush base 12 fixed to the bottom drum 8, a brush holder 13 fixed to the brush base 12 using screws 14, a brush 15 fixed to the brush holder 13, a video head 16, and a head amplifier 17.
The operation of the conventional rotary drum unit shown in FIG. 1 will be described below.
When the top drum 9 is rotated by the motor unit 10, the slip ring 11, the video head 16 and the head amplifier 17 rotate together with the top drum 9. The signal reproduced by the video head 16 is amplified by the head amplifier 17, and the amplified signal is sent through a transformer (rotor not shown) to a transformer (stator not shown) then to a reproduction amplifier (not shown). Power supplied to the head amplifier 17 located within the rotary portion during the reproduction flows from the brush holder 13 to the brush 15, to the slip ring 11 and then to the circuit on the top drum. The position of the brush holder 13 is adjusted and fixed by the screws 14 so that no jumping occurs between the slip ring 11 and the brush 15 during the supply of power. Alternatively, the pressing of the brush is adjusted by a screw 18 so as to provide an adequate contact.
In the above conventional rotary drum unit, each time the brush is mounted or each time the position of the brush is changed due to its wear changing the contact point thereof, the brush contacting force must be adjusted. This requires a complicated adjusting mechanism or adjusting jig.